An electrical circuit breaker operates to engage and disengage a selected branch of an electrical circuit from an electrical power supply. The circuit breaker ensures current interruption, which provides protection to the electrical circuit from unwanted electrical conditions, such as continuous over-current conditions and high-current transients due, for example, to electrical short circuits. Such circuit breakers operate by separating a pair of internal electrical contacts contained within a housing (e.g., molded case) of the circuit breaker.
In many circuit breakers, one electrical contact is stationary, while the other is movable. Conventional circuit breakers may include a moving electrical contact mounted on an end of a moving (e.g., pivotable) contact arm, such that the moving electrical contact moves through a separation path. Contact separation between the moving and stationary electrical contacts may also occur manually, such as by a person moving a handle of the circuit breaker.
In the case of a tripping event (e.g., a short circuit), an armature may be de-latched so as to release the contact arm and open the electrical contacts of the circuit breaker. Under some conditions, tripping may be accomplished by a tripping mechanism wherein the armature is actuated via attraction to a magnet contained in the current path to cause de-latching of a cradle from the armature according to conventional designs.
Some circuit breakers are configured to remain in a closed state for a predetermined period after a current fault occurs wherein the stationary contacts and the moveable contacts remain in contact for a predetermined period after a current fault occurs. If the current fault continues for the predetermined period or if the current exceeds a predetermined amperage, the electrical contacts separate to an open state. These circuit breakers are rated with a current withstand rating that determines their ability to withstand a current fault for a predetermined period. Circuit breakers and other switching devices with high current withstand ratings have a wider range of applications than circuit breakers and switching devices with low current withstand ratings.
Accordingly, there is a need for circuit breakers and electrical switching devices that offer high current withstand ratings.